In recent years, as described in, for example, Appl. Phys. Lett., Vol. 67, Issue 21, pages 3114-3116 (1995) by Stephan Y. Chou, et al., a fine processing technology for transferring a fine structure provided on a mold onto a member to be processed, such as a resin material, a metallic material, or the like, has been developed and has received attention. This technology is called nanoimprinting or nanoembossing, and provides a processing resolving power on the order of several nanometers. For this reason, the technology is expected to be applied to a next-generation semiconductor manufacturing technology in place of a light exposure device, such as a stepper, a scanner, or the like. Further, the technology is capable of effecting simultaneous processing of a three-dimensional structure at a wafer level. For this reason, the technology has been proposed to be applied to a wide variety of fields in manufacturing technologies, and the like, for optical devices, such as photonic crystals, and the like, biochips, such as a μ-TAS (micro total analysis system), etc.
In such a pattern transfer technology using nanoimprinting, e.g., when the technology is used in the semiconductor manufacturing technology, or the like, a minute (fine) structure at a mold surface is transferred onto a work (workpiece) in the following manner.
First, on a substrate (e.g., a semiconductor wafer), as the member to be processed constituting the work, a resin layer of a photocurable resin material is formed. Next, a mold, on which a minute structure having a desired projection/recess pattern is formed, is aligned with the work on an ultraviolet (UV) curable resin material, is filled between the mold and the substrate, followed by irradiation with ultraviolet rays to cure the UV curable resin material. As a result, the minute structure of the mold is transferred onto the resin layer. Then, etching, or the like, through the resin layer, as a mask, is effected to form the minute structure of the mold on the substrate.
Incidentally, in semiconductor manufacturing, it is necessary to effect (positional) alignment of the mold with the substrate. For example, in such a current circumstance that a semiconductor process rule is not more than 100 nm, a tolerance of an alignment error due to an apparatus is said to be several nanometers to several tens of nanometers.
As such an alignment method, e.g., U.S. Pat. No. 6,696,220 has disclosed a technique using different focal lengths with respect to two wavelength light beams, i.e., first and second light beams different in wavelength. In this technique, when a gap between a mold and a substrate has a specific value, a mark provided at a mold surface is formed as an image at a first wavelength on an image pickup device and a mark provided at a substrate surface is formed as an image at a second wavelength, on the same image pickup device. By observing the mold surface mark and the substrate surface mark, in-plane alignment between the mold and the substrate is effected.
Incidentally, with an increasing demand for high-definition fine processing these days, improvements in transfer accuracy and transfer speed by the above-described nanoimprinting are required.
The alignment method disclosed in U.S. Pat. No. 6,696,220, however, is not always satisfactory for such a demand. That is, the alignment method of U.S. Pat. No. 6,696,220 causes the following problem in the in-plane alignment using the mark of the mold and the mark of the substrate.
In the pattern transfer using the nanoimprinting, different from a transfer (exposure) method using a conventional light exposure device, it is necessary to transfer the minute structure provided on the mold in contact with the work (the member to be processed), as described above.
In such a process that the transfer is performed, a contact interface between the mold and the resin material can be placed in an unstable state in a transition period during the contact of the mold with the photocurable resin material of the work. Alternatively, before and after the mold and the photocurable resin material on the work contact each other, various physical conditions with respect to measurement and drive for the alignment can be changed.
The present inventors have come to a recognition that, with respect to a control condition limiting the alignment in the imprinting process, an occurrence of an inconvenience may arise when the control condition is invariant during a period from a non-contact state between the mold and the resin material to a resin material curing process through a contact stage between the mold and the resin material. For example, a case wherein in-plane alignment of a mold with a substrate is performed by observing a mold surface mark and a substrate surface mark is considered.
When alignment feedback control is effected under a control condition for the case of no error, although an error arises in a measurement unit obtained by the observation, an occurrence of a malfunction may arise as a result.